A number of support materials have been suggested for improving ethylene polymerization catalysts made from transition metal compounds promoted by an alkylaluminum compound. Foremost among these are supports containing magnesium. Recently, in British Pat. No. 1,392,099 dried magnesium hexahydroxstannates have been disclosed as carriers for transition metals to form catalyst components which are promoted by aluminum alkyls. The problem with such catalyst component is that although they are alleged to be of excellent yield, preparation can be expensive due to large amounts of transition metal compound and preparation media being required. Additionally, the catalyst components do not produce polymer of a broad molecular weight over a substantially wide range of hydrogen partial pressures. A broad and controllable molecular weight distribution is important to obtain products with a wide range of utilities and the large particle size of the polymer produced in the instant invention is important in product handling and can be particularly important in certain forms of vapor state polymerization.
Now it has been found that good yields of high density polyethylenes and related materials can be obtained at moderate temperatures and pressures by using the solid reaction product of (a) a hydrated magnesium stannate, a lower alkyl titanium (IV) or vanadium (V) alkoxide and an alkylaluminum dichloride and, (b) an aluminum alkyl compound promoter while obtaining a polymer product having a broad and controllable molecular weight distribution and large average particle size.